When in use, sails undergo directional forces along load lines, at or between eyelets, and along the leech and luff. Accordingly, reinforcements may be necessary to distribute the forces, maintain the shape of the sail and to avoid damaging the sail, such as by stretching or tearing.
In many cases, it is also necessary for the fabric to have particular shapes in three dimensions whether for reasons of performance or aesthetics.
Such high-performance, reinforced and shaped sails may be subject to several parameters including commercial criteria. Such criteria may include a fabric that is high-performance (e.g., maintains shape and integrity), is lightweight, and of course, is priced as low as possible.
Many sail-making methods and sail fabrics are known; however, there are some drawbacks.
A basic drawback to many of the known, high-performance reinforced and shaped fabrics presently used for sail manufacture is that the structure of the fabric includes at least three components: 1) a top sheet; 2) reinforcing elements; and 3) a bottom sheet. In general, the reinforcing elements are bonded in a sandwich between the two cover sheets (e.g., polymerized plastic sheets). This type of fabric construction is not only expensive, it is also relatively heavy. Moreover, materials used to form the top and bottom layers, such as polymerized plastic sheets, are semi-rigid and may not allow local deformations.
Some sail manufacturing methods use a mold to create a sail with a three-dimensional shape over the entirety of the sail. Consequently, a mold the same size as the sail is required. Additionally, because the reinforcing yarns are generally positioned as one single piece, the placement of the elements can be very tricky.
Other known methods of sail manufacture include assembling several fabric panels from different cuts, the panels being assembled together by sewing or bonding. With these methods, the seams are fragile and often require reinforcing panels themselves, added by more sewing or boding. Such additional reinforcing panels add to the overall weight of the sail. Moreover, at the location of seams and reinforcing panels, the sail is less flexible than at other regions, which can cause creases, and then fatigue, when the sail takes the desired shape. Such creases are not only unsightly, but also reduce the performance and life of the sail.